The present invention relates generally to sensors including an alarm for sensing the level of pulverant material relative to the level of a liquid within the same container. The invention has particular utility with respect to sensing the level of salt within a salt-brine tank of a household water softener.
Household water softeners generally include a vessel containing an ion exchange resin intended to remove calcium and other minerals from a supply of water used within the household. From time to time, generally once every day or two, it becomes necessary to recharge the ion exchange resin so it can continue to perform its intended function. The recharging is accomplished by introducing a brine solution into the resin bed whereby a reverse ion exchange takes place freeing the calcium and other undesired ions which can then be flushed from the system and down the drain. Once the system is recharged, an amount of water is introduced into a tank containing pellet or particulate salt to form a new supply of brine for the next recharge cycle.
On introduction of the fresh water into contact with the salt, a portion of the salt dissolves in the water thereby lowering the level of the salt within the salt-brine tank. After a number of recharged cycles, it becomes necessary to add salt to the salt-brine tank. Since the recharging generally occurs automatically, a householder often gives little thought to the operation of the water softener system. Often, the householder discovers that a water softener is out of salt only when sensing that the water is no longer as soft as desired It is therefore an object of the present invention to alert a householder when the level of salt within the salt-brine tank falls below a desired minimum level and, in particular, below the maximum water level within the salt-brine tank.
On occasion, a water softener runs out of salt while the householder is absent for an extended period of time such as during a family vacation, or the like. Were an alarm system designed to sound continuously upon activation, such an extended absence might cause the battery to run down and the alarm to cease operation before the return of the householder. It is therefore an object of the Present invention to Provide an alarm which will periodically sound a short alarm over an extended period of time to alert the householder. It is a further object to minimize the current through the sensor during an alarm condition to extend battery life and to preserve sensor integrity.